My fiance was texting another girl inappropriately, should I forgive him and work things out?

This is the first time it's happened. It was just one day of texting because one of his friends gave her his number, it happens to be his boss's daughter. He didn't deny it when I asked and he cried and apologized and said it was nothing more than those texts and he doesn't know why he did it, that it was foolish and made him realize he's where he wants to be and that it scared him cause he thought he was going to lose me. He's never dated the girl or hooked up with her or talked to her before, just this one day he swears it'll never happen again and I'm the only girl for him and he still wants to marry me in 2 weeks. I don't know what to do cause it hurts really bad

Not all errors in judgment are accidental. He should indeed answer for his behaviors, but even if he purposefully acted, it is not necessarily to say that he himself will not see it as a senseless mistake.

We can't say that for sure. Let's not try to take blind guesses; a lot of people catch their partners in "questionable scenarios" and work through it. It is not our job to inject venom into the situation and make it worse. As for his behavior, no one is denying it was a conscious decision, thus why he should answer for it, but telling her to abandon everything because of it is kind of extreme. Perhaps if he had a track record of the behavior I'd agree.